1. Field of the Invention
The present invention relates generally to orthotic designs for lower limb orthopedic devices. The present invention relates more specifically to an orthotic system and method utilizing hydrostatic compression of soft tissue to remove the load bearing forces of the knee and/or distal tibia, talus, and heel up to 100%.
2. Description of the Related Art
There are a number of medical conditions in which load bearing on an affected structure is contraindicated. Injuries such as fractures of the talus, comminuted fractures of the distal tibia or calcaneus, osteomyelitis infections, avascular necrosis of the talus, ulcerations, post surgical infections and some other acute conditions can be adversely impacted under the stress of weight bearing.
In the past, severe conditions of the knee, distal tibia, talus, or calcaneus may have been treated with immobilization and partial unloading by use of plaster-of-paris casts. These plaster casts, however, would be heavy and uncomfortable for the patient. More recently, either custom fabricated or prefabricated orthoses have been prescribed by physicians as a more lightweight and comfortable alternative to plaster casts. These orthoses also have the advantage of the capability to be removed by the patient at any time.
However, prior art custom fabricated and prefabricated orthoses both have their drawbacks. Prior art prefabricated orthoses are not capable of withstanding long periods of use, are very bulky which eliminates the possibility of normal footwear, and are not capable of 100% unloading of the desired structures. Prior art custom orthoses are capable of longer lengths of use and may be used with normal footwear, but these orthoses are very difficult to fabricate properly. Moreover, these designs tend to rely on achieving a purchase on proximal bones, rather than soft tissue, making them difficult to tolerate for extended periods.
A commonly prescribed prefabricated orthosis is the Zero G. While the Zero G is capable of 100% unloading of the distal tibia, ankle and heel, it is not applicable toward conditions of the knee. Also, this brace is very bulky and will not allow the use of normal footwear on the braced side. The Zero G is designed for temporary use of just a few months and will not hold up to the rigors of every day activity.
One of the most frequently prescribed custom orthoses to offload the distal tibia, ankle, and heel is the patellar tendon bearing (PTB) orthosis. The PTB orthosis is a well known design which transfers weight through the patellar tendon and onto the orthopedic device similar to the approach used in below knee prosthetic devices. PTBs are difficult to fabricate and often not tolerated due to the pressures and forces needed to achieve the desired outcome, removing all load bearing forces of the distal tibia and below. In prosthetics, the PTB type prosthesis is better tolerated as these forces are only present in weight bearing. As soon as weight is removed from the extremity the pressures dissipate. In orthotics this is not the case.
While the Zero G, PTB orthosis, and other such prior art devices can sometimes be successful in treating these types of conditions, they all have major drawbacks. Also, the majority of options currently available are only applicable to the lower leg and none are capable of 100% unloading of the knee during ambulation.
In many situations complete unloading may be recommended but the patient may not have a lifestyle that allows for such limited ambulation, and because there is currently no orthopedic device available that allows for ambulation while unloading the knee, distal tibia, talus, or heel up to 100% without major drawbacks, there is need for a device specifically designed to unload the desired structures up to 100% with more benefits and fewer drawbacks than prior art designs.